The New York Islanders, unable to open the champagne on Tuesday, popped the cork tonight.

Goals by Butch Goring and Wayne Merrick 25 seconds apart early in the first period made the rest of the eveing a formality as the Islanders whipped the Minnesota North Stars, 5-1, and took the best of seven Stanley Cup final series by a 4-1 margin.

Goring scored twice for the Islanders, continued to excel as a penalty killer and forechecker and was honored with the Conn Smythe Trophy as the most valuable player of the playoffs.

It was the Islanders' second straight Cup and they won it convincingly, losing only three of 18 playoff games after finishing first during the regular season.

"This was a little bit better than the last one, because this time I had the ups and downs with them and felt more like part of them," said Goring, acquired in a trade with Los Angeles a month before the 1980 playoffs began. "Last year I came so late that I never really had time to do anything but play. Now I know all these guys, and it means so much more."

"We were supposed to win and we did," said Merrick, whose goal was the eventual game winner. "We had to overcome a lot of pressure and to do what we did is the greatest thing I've ever seen."

"We're a much better team this year, much stronger," said goalie Bill Smith, who played all but one of the 18 playoff games."This was the kind of team you couldn't rattle. Last year we got rattled when we got behind, but this year if we were two goals down, we just said, 'So what?' and went out and won."

If the 15,008 fans had been through it all before, they seemed to enjoy the feeling of victory just as much as last year. Champagne bottles were opened in the stands as the clock wound down and fans jumped onto the ice to hug their heroes, battling security guards in what turned out to be the most competitive struggle of the night.

Smith stickhandled behind the net for the last 10 seconds, then his teammates piled on him in joyous abandon.

Denis Potvin, the Islander captain who missed much of the game with a groin pull, skated slowly around the ice carrying the Stanley Cup, then he permitted each of his teammates a few victory strides.

Afterward, wives, friends and gate crashers turned the Islander dressing room into a wall-to-wall party despite the efforts of security personnel to control the influx.

It was almost as though all concerned had been waiting two days to explode, since the Islanders were beating, 4-2, in Minnesota Tuesday night, forcing this extra night of labor.

There was only one doubtful moment tonight, just a few seconds before Goring's power play goal sent the Islanders ahead to stay.

With Minnesota's Brad Palmer off for holding, Potvin flubbed a pass from behind his goal line and the North Stars' Mike Polich took control in front of the New York net. Polich fell over Smith without releasing a shot.

"Fortunately, he was too close to me," Smith said. "I knew he was too close, so I came out and I ended up tripping him."

When play moved to the other end, Islander Bob Bourne picked off a poor pass by defenseman Greg Smith and fed Goring, who hit from the right-wing circle at 5:12.

The fans were still screaming when John Tonelli's pass from behind the Minnesota net at 5:37 was quickly converted into a 2-0 lead by Merrick.They might as well have stopped right there and handed over the Cup.

Goring scored again at 10:03, on a setup by Clark Gillies, before Steve Christoff scored the only Minnesota goal.

In the second period, the Islanders had an apparent goal by Goring disallowed, because referee Bryan Lewis blew his whistle an instant before the puck entered the net. Lewis was protecting North Star Kevin Maxwell, shaken up on a spin into the boards.

Bourne made it 4-1 in the last minute of the period, then Mike McEwen closed the scoring with 2:54 to play. Bryan Trottier, who had played wit a shoulder separation since his second shift Tuesday night, assisted on Bourne's goal to extend his point-scoring streak to a record 25 playoff games over two seasons.

Despite the joy surrounding this series success, Smith said the highlight of the playoffs was the semifinal sweep of the hated Rangers.

"Yeah, that was the best, because they had a lot to say," Smith said. "We're the kind of guys who don't knock a hockey team. How about (Bob) Gainey in Montreal, he never said a good word about us all season. I wonder what he's saying tonight."

Gainey had referred to the Islanders as a "third-place" team. Tonight, however, as their fans indicated loudly and frequently, they definitely were No. 1.